U.S. patent application number 12/526288 was filed with the patent office on 2010-12-16 for manufacturing method for display device and display device.
This patent application is currently assigned to SHARP KABUSHIKI KAISHA. Invention is credited to Yoshimasa Chikama, Tohru Okabe.
Application Number | 20100316870 12/526288 |
Document ID | / |
Family ID | 40001969 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100316870 |
Kind Code |
A1 |
Okabe; Tohru ; et
al. |
December 16, 2010 |
MANUFACTURING METHOD FOR DISPLAY DEVICE AND DISPLAY DEVICE
Abstract
A method for manufacturing a display device includes a first
step of preparing a first substrate which has a first area to be
etched and a second area located at a periphery of the first area
and which has a display element on its surface, a second step of
etching and removing the first area of the first substrate, a third
step of forming a second substrate on a surface of the first
substrate that is opposite to the surface on which the display
element is located, and a fourth step of removing the second area
of the first substrate.
Inventors: |
Okabe; Tohru; (Osaka-shi,
JP) ; Chikama; Yoshimasa; (Osaka-shi, JP) |
Correspondence
Address: |
SHARP KABUSHIKI KAISHA;C/O KEATING & BENNETT, LLP
1800 Alexander Bell Drive, SUITE 200
Reston
VA
20191
US
|
Assignee: |
SHARP KABUSHIKI KAISHA
Osaka-shi, Osaka
JP
|
Family ID: |
40001969 |
Appl. No.: |
12/526288 |
Filed: |
January 11, 2008 |
PCT Filed: |
January 11, 2008 |
PCT NO: |
PCT/JP2008/050227 |
371 Date: |
August 7, 2009 |
Current U.S.
Class: |
428/337 ;
216/4 |
Current CPC
Class: |
G02F 1/1303 20130101;
Y10T 428/266 20150115; G02F 1/133302 20210101; G02F 1/1333
20130101 |
Class at
Publication: |
428/337 ;
216/4 |
International
Class: |
B32B 33/00 20060101
B32B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2007 |
JP |
2007-129054 |
Claims
1-11. (canceled)
12. A method for manufacturing a display device comprising: a first
step of preparing a first substrate which has a first area to be
etched and a second area located at a periphery of the first area
and which has a display element on its surface; a second step of
etching and removing the first area of the first substrate; a third
step of forming a second substrate on a surface of the first
substrate that is opposite to the surface on which the display
element is located; and a fourth step of removing the second area
of the first substrate.
13. The method of claim 12, wherein in the second step, a thickness
of the first substrate is reduced such that the first substrate is
a thin film.
14. The method of claim 13, wherein in the second step, the
thickness of the first substrate is etched to be about 0.05 mm or
less.
15. The method of claim 12, wherein in the first step an etch stop
layer is formed between the first substrate and the display
element.
16. The method of claim 15, wherein the etch stop layer is formed
by a thermal CVD method.
17. The method of claim 15, wherein the etch stop layer is made of
a polycrystalline silicon material.
18. The method of claim 12, wherein the second area surrounds the
first area; a depression is formed in the first substrate by
etching and removing the first area in the second step; and the
second substrate is formed in the depression in the third step.
19. The method of claim 12, further comprising a step of forming a
laminated substrate by laminating a counter substrate which has a
first area to be etched and a second area located at a periphery of
the first area, to the first substrate prepared in the first step,
with a display media interposed between the counter substrate and
the first substrate, wherein the first area of the first substrate
and the first area of the counter substrate of the laminated
substrate are etched in the second step.
20. A display device manufactured by the method of claim 12.
21. The display device of claim 20, wherein the first substrate is
made of a moisture impermeable material.
22. A display device manufactured by the method of claim 15,
wherein the etch stop layer is made of a moisture impermeable
material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for manufacturing
a display device and a display device.
[0003] 2. Description of the Related Art
[0004] Display devices in which a display element or the like is
provided on a thin flexible substrate such as a plastic substrate
are currently receiving attention because they are considerably
superior, in terms of lightweight and flexibility, to display
devices which use a glass substrate or a silicon substrate.
Techniques for providing a display element or the like on a
flexible substrate include a direct method in which the display
element or the like is directly provided on the flexible substrate.
The techniques also include a transfer method in which the display
element or the like is temporarily provided on a glass substrate, a
silicon substrate, or the like and later transferred to a flexible
substrate (Japanese Laid-Open Patent Application Publication No.
10-125929, for example).
[0005] However, according to the above-described conventional
transfer method, the display device is very weak in strength, and
once the glass substrate, silicon substrate, or the like is
removed, it is difficult to carry the display device.
[0006] To prevent this, a two-step process is carried out in which
a thick support substrate is temporarily bonded to the front side
of a display device, and then, the support substrate is separated
or etched; after that, a flexible substrate is formed on the back
side of the display device, and then, the support substrate is
again separated or etched.
[0007] This two-step process requires more support substrates and
also requires attachment and detachment processes for the support
substrates. Accordingly, it is not only that costs are increased,
but also that yields and quality are reduced, because the front
side of the display device on which fine patterns are formed is
exposed to an adhesive and an etchant.
SUMMARY OF THE INVENTION
[0008] In view of the above, preferred embodiments of the present
invention provide a display device manufacturing method which
enables a display element to be easily formed on a substrate at a
low cost without reducing its quality, and also provide a display
device.
[0009] A method for manufacturing a display device according to a
preferred embodiment of the present invention includes a first step
of preparing a first substrate which has a first area to be etched
and a second area located at a periphery of the first area and
which has a display element on its surface, a second step of
etching and removing the first area of the first substrate, a third
step of forming a second substrate on a surface of the first
substrate that is opposite to the surface on which the display
element is located, and a fourth step of removing the second area
of the first substrate.
[0010] Unlike conventional transfer methods, the above-described
structure according to a preferred embodiment of the present
invention does not require an extra support substrate to which a
display element is temporarily bonded, nor does it require removal
of the support substrate. Thus, the display element can be easily
formed on a substrate at a low cost. Further, etchant or the like
is prevented from flowing from an etching side to a substrate
surface and reaching to the display element, because only the first
area surrounded by the second area is etched. Thus, yield and
quality reduction of the display device can be effectively
prevented. Moreover, unlike conventional direct methods, the
display element can be formed on the first substrate at a high
temperature by using, as the first substrate, a glass substrate or
a silicon substrate which exhibits high strength, and therefore, a
high-performance display device can be manufactured.
[0011] According to various preferred embodiments of the present
invention, it is possible to provide a display device manufacturing
method according to which a display element can be easily formed on
a substrate at a low cost, and also to provide a display
device.
[0012] Other features, elements, steps, characteristics and
advantages of the present invention will become more apparent from
the following detailed description of preferred embodiments of the
present invention with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross-sectional view of a glass substrate for
illustrating a first substrate formation process according to
Preferred Embodiment 1 of the present invention.
[0014] FIG. 2 is a plan view of a glass substrate on which a first
area and a second area according to Preferred Embodiment 1 of the
present invention are formed.
[0015] FIG. 3 is a cross-sectional view of a glass substrate for
illustrating an etch protection area formation process and an
etching process according to Preferred Embodiment 1 of the present
invention.
[0016] FIG. 4 is a cross-sectional view of a glass substrate which
is etched by an etching process according to Preferred Embodiment 1
of the present invention.
[0017] FIG. 5 is a cross-sectional view of a glass substrate having
a depression after an etch protection area removal process
according to Preferred Embodiment 1 of the present invention.
[0018] FIG. 6 is a cross-sectional view of a glass substrate having
a depression in which a resin substrate is formed by a second
substrate formation process according to Preferred Embodiment 1 of
the present invention.
[0019] FIG. 7 is a cross-sectional view of a TFT substrate from
which a second area is separated by a second area removal process
according to Preferred Embodiment 1 of the present invention.
[0020] FIG. 8 is a cross-sectional view of glass substrates for
illustrating an etch protection area formation process and an
etching process for a laminated substrate according to Preferred
Embodiment 2 of the present invention.
[0021] FIG. 9 is a cross-sectional view of a laminated substrate
having a depression after an etch protection area removal process
according to Preferred Embodiment 2 of the present invention.
[0022] FIG. 10 is a cross-sectional view of a liquid crystal
display panel from which a second area is separated by a second
area removal process according to Preferred Embodiment 2 of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Example Preferred Embodiments
[0023] Preferred embodiments of the present invention are
hereinafter described in detail using the drawings. However, the
present invention is not limited to these preferred embodiments
described below.
Preferred Embodiment 1
[0024] A TFT (thin film transistor) substrate is described in
detail as an example of a display device according to Preferred
Embodiment 1 of the present invention, by using drawings.
Method for Forming TFT Substrate 10
First Substrate Formation Process
[0025] First, a glass substrate 11 (first substrate) which, for
example, has a substrate size of approximately 365.times.460 mm and
a thickness of about 0.7 mm is prepared as shown in FIG. 1. Here,
the first substrate may be made of any material, but a moisture
impermeable material is particularly preferable.
[0026] Next, a high-performance TFT 12 is formed on the glass
substrate 11 using a known technique.
[0027] As shown in FIG. 2, an area where the TFT 12 is formed
(first area 13) is surrounded by an area provided along the
periphery of the substrate and having a width of approximately 50
mm, for example, where the TFT is not formed (second area 14). An
alignment pattern, a test pattern or others used only when the TFT
12 is formed is provided in the second area 14.
Etch Protection Area Formation Process
[0028] Next, as shown in FIG. 3, an etching mask 15 (etch
protection area) is formed, using a dry resist or the like, in the
second area 14 of the surface of the glass substrate 11 that is
opposite to the surface on which the TFT 12 is formed. At this
time, only the first area 13 is exposed at the surface of the glass
substrate 11 that is opposite to the surface on which the TFT 12 is
formed.
Etching Process
[0029] Next, the surface of the glass substrate 11 that is opposite
to the surface on which the TFT 12 is formed is etched using an
etchant. Any kind of etchant can be used, but a hydrogen fluoride
based etchant by which glass can be easily etched is particularly
suitable. Arrows in FIG. 3 indicate the direction of etching. Wet
etching is preferable for this etching because a physical etching
method, such as polishing, may damage the TFT 12. Since only the
first area 13 surrounded by the second area 14 provided with the
etching mask 15 is etched, it is possible to prevent etching
variations due to penetration of the etchant from the periphery of
the glass substrate 11 which occurs when the entire surface of the
glass substrate 11 is etched as in conventional transfer methods.
Hence, the thickness of the glass substrate 11 can be effectively
reduced to about 0.05 mm or less as shown in FIG. 4. Only wet
etching is described here, but dry etching, such as plasma etching,
may be used to increase the etching accuracy. The glass substrate
11 obtained by melting is known to exhibit very superior moisture
barrier characteristics, and the display device can be used as a
high-performance moisture barrier film by reducing this glass
substrate 11 in thickness of about 0.01 mm or less, for example.
Reducing the glass substrate to some extent without completely
removing the glass substrate by etching is very effective
particularly when a device such as an organic EL element which
requires extremely high moisture barrier characteristics of about
10.sup.-6 g/m.sup.2day or more is formed on a highly permeable
flexible substrate such as a plastic substrate.
[0030] The entire first area 13 of the glass substrate 11 can be
etched if an etch stop layer is formed on the entire surface of the
glass substrate 11 before the TFT 12 is formed. Moisture
impermeable materials whose wet etch selectivity ratio to a glass
substrate is high are preferable as a material for the etch stop
layer. Transparent materials for the etch stop layer may preferably
include an Si.sub.3N.sub.4 film and a Ta.sub.2O.sub.5 film formed
by a thermal CVD method, for example. In the case of a
self-luminous element such as an organic EL, the etch stop layer
may be a stacked film of polycrystalline silicon and an insulating
film, having a much higher wet etch selectivity ratio. The etch
stop layer is a good-quality film, if formed on the glass substrate
in a clean state and at a high temperature. Thus, the etch stop
layer can be far superior to a moisture barrier film formed on a
substrate which has low resistance to heat and which has
asperities, such as a plastic substrate.
Etch Protection Area Removal Process
[0031] Next, as shown in FIG. 5, the etching mask 15 provided in
the second area 14 is removed. The thickness of only the first area
13 is reduced by etching, and then, the etching mask 15 provided in
the second area 14 is removed. As a result, a depression 17 is
formed in the glass substrate 11.
Second Substrate Formation Process
[0032] Next, as shown in FIG. 6, a resin material which, for
example, has high viscosity is supplied into the depression 17 of
the glass substrate 11, and after that, the resin material is baked
to form a resin substrate 18 (second substrate).
Second Area Removal Process
[0033] Next, as shown in FIG. 7, the second area 14 of the glass
substrate 11 is separated from the first area 13 using laser light
or the like, thereby forming a high-performance TFT substrate 10 on
the thin, flexible substrate.
Structure of TFT Substrate 10
[0034] Now, a structure of the TFT substrate 10 formed by the above
method is described.
[0035] The TFT substrate 10 includes the resin substrate 18 (second
substrate) and the glass substrate 11 (first substrate) which is
formed on the resin substrate 18 and which has the TFT 12.
[0036] The resin substrate 18 is made of a resin material having
high viscosity, and the glass substrate 11 formed on the resin
substrate 18 has a thickness of about 0.05 mm or less, for example.
Thus, the TFT substrate 10 exhibits good flexibility. In addition,
moisture can be effectively prevented from passing through the
resin substrate 18 because the glass substrate 11 is interposed
between the resin substrate 18 and the TFT 12.
Preferred Embodiment 2
[0037] Now, a liquid crystal display panel in which a TFT substrate
and a CF (color filter) substrate (counter substrate) are laminated
together is described in detail as an example of a display device
according to Preferred Embodiment 2 of the present invention, by
using drawings. Structural elements similar to those in Preferred
Embodiment 1 are labeled with the same characters.
Method for Forming Liquid Crystal Display Panel 20
TFT Substrate Formation Process
[0038] A glass substrate 11 (first substrate) which, for example,
has a substrate size of approximately 365.times.460 mm and a
thickness of about 0.7 mm is prepared as shown in FIG. 8.
[0039] Next, a high-performance TFT 12 is formed on the glass
substrate 11 using a known technique.
[0040] Here, an area where the TFT 12 is formed is surrounded by an
area provided along the periphery of the substrate and having a
width of approximately 50 mm where the TFT 12 is not formed, as
shown in FIG. 2 of Preferred Embodiment 1. The area where the TFT
12 is formed is referred to as a first area 13, and the area where
the TFT 12 is not formed is referred to as a second area 14.
CF Substrate Formation Process
[0041] Next, a glass substrate 21 (first substrate) which has a
substrate size of approximately 365.times.460 mm and a thickness of
about 0.7 mm is prepared by the same process as the above TFT
substrate 10 formation process, and then, a counter substrate
element 22, such as a color filter layer and a counter electrode,
is formed on the surface of the glass substrate 21 to obtain a CF
substrate 31.
[0042] Here, an area where the counter substrate element 22 is
formed is surrounded by an area provided along the periphery of the
substrate and having a width of approximately 50 mm where the
counter substrate element 22 is not formed, as shown in FIG. 2 of
Preferred Embodiment 1. The area where the counter substrate
element 22 is formed is referred to as a first area 23, and the
area where the counter substrate element 22 is not formed is
referred to as a second area 24.
Substrate Laminating Process
[0043] Next, the TFT substrate 10 and the CF substrate 31 are
laminated together using an epoxy-based resin 25 or the like such
that the TFT 12 and the counter substrate element 22 face each
other. A liquid crystal molecule is supplied into a space between
the TFT 12 and the counter substrate element 22, thereby obtaining
the laminated substrate 30.
Etch Protection Area Formation Process
[0044] Next, etching masks 15 (etch protection areas) are formed,
using a dry resist or the like, in the respective second areas 14
and 24 of the surfaces of the glass substrates 11 and 21 that are
opposite to the surfaces on which the TFT 12 and the counter
substrate element 22 are formed. At this time, only the first areas
13 and 23 are exposed at respective surfaces of the glass
substrates 11 and 21 that are opposite to the surfaces on which the
TFT 12 and the counter substrate electrode 22 are formed.
Etching Process
[0045] Next, the surfaces of the glass substrates 11 and 21 that
are opposite to the surfaces on which the TFT 12 and the counter
substrate element 22 are formed are etched until the glass
substrates 11 and 21 have a thickness of about 0.05 mm or less, for
example, by using a hydrogen fluoride based etchant by which glass
can be easily etched. Arrows in FIG. 8 indicate the direction of
etching.
Etch Protection Area Removal Process
[0046] Next, the etching masks 15 provided in the second areas 14
and 24 are removed. The thicknesses of only the first areas 13 and
23 are reduced by etching, and then, the etching masks 15 provided
in the second areas 14 and 24 are removed. As a result, depressions
17 and 27 are formed in the glass substrates 11 and 21,
respectively.
Second Substrate Formation Process
[0047] Next, a resin material which, for example, has high
viscosity is supplied into each of the depressions 17 and 27 of the
glass substrates 11 and 21, and after that, the resin material is
baked to form resin substrates 18 and 28 (second substrates).
Second Area Removal Process
[0048] Next, as shown in FIG. 10, the second areas 14 and 24 of the
glass substrates 11 and 21 are separated from the first areas 13
and 23 using laser light or the like, and after that, a
predetermined process, such as a polarizing plate formation process
and a protection film formation process, is carried out, and as a
result, a high-performance liquid crystal display panel 20 can be
formed on the thin, flexible substrate.
Structure of Liquid Crystal Display Panel 20
[0049] Now, a structure of the liquid crystal display panel 20
formed by the above method is described.
[0050] The liquid crystal display panel 20 includes the laminated
substrate 30 in which the TFT substrate 10 and the CF substrate 31
are laminated together, with the liquid crystal molecule 29 and a
spacer (not shown) interposed therebetween, and includes a
polarizing plate, a protection film and others (not shown) as shown
in FIG. 10.
[0051] The TFT substrate 10 and the CF substrate 31 respectively
includes the resin substrates 18 and 28 (second substrates) and the
glass substrates 11 and 21 (first substrates) which are formed on
the resin substrates 18 and 28 and which have the TFT 12 and the
counter substrate element 22, respectively.
[0052] The resin substrates 18 and 28 are made of a resin material
having high viscosity, and the glass substrates 11 and 21 formed on
the resin substrates 18 and 28 have a thickness of about 0.01 mm or
less, for example. Thus, the TFT substrate 10 and the CF substrate
31 exhibit good flexibility. In addition, moisture can be
effectively prevented from passing through the resin substrates 18
and 28 because the glass substrates 11 and 21 are interposed
between the resin substrate 18 and the TFT 12 and between the resin
substrate 28 and the counter substrate element 22.
[0053] Elements formed in the first areas 13 and 23 are not limited
to the above TFT 12 and the counter substrate element 22 such as
CF, but may be a piezoelectric element and a wiring pattern.
[0054] In Preferred Embodiments 1 and 2, examples utilizing LCDs
(liquid crystal displays) as display devices have been described.
However, PDs (plasma displays), PALC (plasma addressed liquid
crystal) displays, organic EL (organic electro luminescence)
displays, inorganic EL (inorganic electro luminescence) displays,
FEDs (field emission displays), SEDs (surface-conduction
electron-emitter displays), etc. may be utilized as display
devices.
Operations, Advantages and Effects
[0055] Operations, advantages and effects of preferred embodiments
of the present invention are now described.
[0056] A method for forming the TFT substrate 10 includes a first
step of preparing a glass substrate 11 which has a first area 13 to
be etched and a second area 14 located at a periphery of the first
area 13 and which has a TFT 12 on its surface, a second step of
etching and removing the first area 13 of the glass substrate 11, a
third step of forming a resin substrate 18 on a surface of the
glass substrate 11 that is opposite to the surface on which the TFT
12 is located, and a fourth step of removing the second area 14 of
the glass substrate 11. Unlike conventional transfer methods, the
above structure does not require an extra support substrate to
which the TFT 12 is temporarily bonded, nor does it require a
removal of the support substrate. Thus, the TFT 12 can be easily
formed on a substrate at a low cost. Further, etchant or the like
is prevented from flowing from an etching side to a substrate
surface and reaching to the TFT 12, because only the first area 13
surrounded by the second area 14 is etched. Thus, reduction in
yield and quality of the TFT substrate 10 can be effectively
prevented. Moreover, unlike conventional direct methods, the TFT 12
can be formed on the glass substrate 11 at a high temperature by
using, as the glass substrate 11, a glass substrate or a silicon
substrate which exhibits high strength, and therefore, a
high-performance TFT substrate 10 can be manufactured.
[0057] According to the method for forming the TFT substrate 10,
the thickness of the glass substrate 11 is reduced in the second
step such that the glass substrate 11 is a thin film. According to
this structure, the glass substrate 11 can be a support until the
resin substrate 18 is formed in the third step, and at the same
time a flexible display device can be obtained.
[0058] According to the method for forming the TFT substrate 10,
the thickness of the glass substrate 11 is etched to be about 0.05
mm or less, for example. According to this structure, the TFT
substrate 10 can exhibit good flexibility.
[0059] According to the method for forming the TFT substrate 10, an
etch stop layer is formed between the glass substrate 11 and the
TFT 12. According to this structure, the glass substrate 11 can be
completely removed by etching, and thus, the thickness of the etch
stop layer can be accurately controlled. Thus, the etch stop layer
can be a support until the resin substrate 18 is formed in the
third step, and at the same time a flexible display device can be
obtained. Further, the etch stop layer can be formed on the glass
substrate 11 which has high resistance to heat and a very flat
surface, and therefore, a thin etch stop layer formed under good
conditions can be used in the display device. In addition, the etch
stop layer may be formed by a thermal CVD method. Thus, an
Si.sub.3N.sub.4 film and a Ta.sub.2O.sub.5 film whose etch
selectivity ratios to glass are very high can be formed in good
conditions. At this time, the etch stop layer is transparent, and
thus, there is no possibility that light is prevented from passing
through. Moreover, the etch stop layer may be made of a
polycrystalline silicon material. The etch selectivity ratio of
this material to glass is very high, and thus, the thickness of the
etch stop layer can be reduced.
[0060] According to the method for forming the TFT substrate 10,
the second area 14 surrounds the first area 13, and a depression 17
is formed in the glass substrate 11 by etching and reducing the
thickness of the first area 13 in the second step, and the resin
substrate 18 is formed in the depression 17 in the third step.
According to this structure, the display device can be formed
efficiently and accurately only in an area where the display device
needs to be formed.
[0061] The method for forming the TFT substrate 10 further includes
the step of forming a laminated substrate 30 by laminating a CF
substrate 31 which has a first area 13 to be etched and a second
area 14 located at the periphery of the first area 13, to the glass
substrate 11 prepared in the first step, with a liquid crystal
molecule 29 interposed between the CF substrate 31 and the glass
substrate 11, wherein the first area 13 of the glass substrate 11
and the first area 13 of the CF substrate 31 of the laminated
substrate 30 are etched in the second step. According to this
structure, a liquid crystal display element in which two substrates
are laminated together can be easily formed at a low cost without
reducing its quality.
[0062] The liquid crystal display panel 20 is formed by the above
fabrication method and thus can be easily formed at a low cost
without reducing the quality of the liquid crystal display panel
20.
[0063] The glass substrate 11 of the liquid crystal display panel
20 is made of a moisture impermeable material. This structure can
prevent moisture from passing through the glass substrate 11 and
reaching to the TFT 12. Thus, reduction in quality of the liquid
crystal display panel 20 can be effectively prevented.
[0064] The etch stop layer of the liquid crystal display panel 20
is made of a moisture impermeable material. According to this
structure, a quality etch stop layer, which is difficult to form
directly on the resin substrate 18, can be formed on the resin
substrate 18, and thus, moisture can be significantly prevented
from passing through the etch stop layer and reaching to the TFT
12. Accordingly, reduction in quality of the liquid crystal display
panel 20 can be effectively prevented.
[0065] As described in the above, the present invention relates to
a method for manufacturing a display device and to a display
device.
[0066] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *